Enhanced and rapid remediation of chlorpyrifos from aqueous phase by amine modified mesoporous silica SBA-15: A systematic investigation on sorption kinetics and mechanistic studies

Abstract

Pesticides have become a necessary remedy of contemporary agricultural methods. However, the release of excess pesticides to the water bodies is a growing concern worldwide. Chlorpyrifos (CP), an organophosphate based pesticide used for nearly 50,000 tonnes per year globally, has significantly affected the ecosystem. Herein, we have reported that (3-Aminopropyl)triethoxysilane functionalized SBA-15 (ASBA-15) as an efficient adsorbent to remove CP from its aqueous solution to an extent of 1814 mg g⁻¹ within 20 min. The uptake behavior was studied in detail as a function of adsorbent dosage, contact time, and concentration levels of CP. The adsorption findings were well-fitted into the Langmuir isotherm model and pseudo-second-order kinetics. The estimated values of ΔH⁰ and ΔS⁰ revealed the exothermic and spontaneous nature of the process. The XRD reflections between 2 $\theta$ = 0.90–1.8^o, surface area in the ranges of 781–435 m² g⁻¹ and pore diameters between 7.2 and 6.0nm indicated the mesoporous as well as stable structure for SBA-15 and ASBA-15 materials at different stages of studies. FT IR studies evidenced the presence of the ‒NH group at 1541 cm⁻¹ in ASBA-15. Thermogravimetric analysis results supported the grafting of the ‒NH group onto ASBA-15 as well as the efficient adsorption of CP. The appearance of characteristic vibration of CP at 1513 cm⁻¹ in CP@ASBA supported the entrapment of CP within ASBA-15. The adsorption and desorption of CP by ASBA-15 were accomplished for five cycles without significant mass loss, which demonstrated the reusability, stability and reversible nature of the material.